Actually, God Mode encounter is the most profitable of "bonuses". If you kill it, you get 10 k. Much less interesting is "deal as much damage as possible", I personally get 3k on average. Invisi mech is also laughable, but bullion is bullion, as they say...

Actualy deal as much dmg as possible is nice, you can see how much dmg you deal.Me personaly, with a breacker-nova mech, average about 7-9k, in it.The "god mode" challenge is also good, since you can see again the dmg output of your build.The "invisi mech" yeah that is useless, it usualy pops up the shield and it generates a glow on the floor so you always know where it is. Also the wepons give way his position, in range/ out of range etc, and it's pretty easy to beat.

Damage challenge - You can check the how much damage your Mech doesInvisible Mech challenge - Useless , not much FunGod Mode - I like it. The classic God Mode challenge used to be much better , now its not a big deal